Black pyramids

[Captainpasta]

I have completed the brain trials like 3 times already and i have never managed to get the "black pyramids remains"
It's sending me nuts
I have used the tank's high-power laser cannon
Am i doing something wrong? Am i supposed to use piercing damage ? Or is my savefile just fucking around with the last updates and i have to restart ?

[Vakrug]

In order to get pyramid remains you have to destroy the portal inside. A chemical grenade will do the job, but any strong explosion is enough.
Also there should be event that will give to you 1 pyramid remains and tells about necessity to wait for special zombies to spawn.